Cooling element

ABSTRACT

A cooling element includes two layers of a foil material, fastened to one another by welding connections such that a compartment closed for liquid is formed between them and at least one of the layers is vapor-transmitting over at least a portion of its surface area. The two layers of foil material include thermoplastic plastic, or polyurethane, polypropylene, or polyethylene. Alternatively or additionally, the layers of foil material include a weldable material at least at sides that face one another, and the connections are formed by welded connections. The layers of foil material and the intermediate layer may be manufactured from thermoplastic plastics.

The present invention relates to a cooling element comprising two layers of a foil material that may or may not be flexible, said two layers of foil material being fastened to one another by means of welding connections such that a compartment closed for liquid is formed between them, wherein at least one of the layers is vapour-transmitting over at least a portion of its surface area.

Similar cooling elements with a welded construction are known, for example, from the UK Patent Application GB 2 348 796 A, in which document a personal cooling garment has an inner layer and outer layer defining a confined space or bladder therebetween for containing liquid water. The layers are thin materials impermeable to both air and liquid water yet permeable to water vapour. No water-retaining, vapour-releasing material between the layers, such as a wick, is disclosed in GB 2 348 796 A.

Cooling elements with a multi-layer construction, either or not welded, are used, for example, in bottle holders, bags or rucksacks in order to keep objects cool, such as bottles containing beverages. Sometimes such a cooling element is used for keeping parts of a human body, such as a damaged bundle of muscles, relatively cool.

The cooling effect is derived from the evaporation of water, for which a supply of heat is required. Since the arising vapour is discharged through the moisture-transmitting foil material, the evaporation may continue as long as any moisture is present in the liquid-absorbing, vapour-releasing material.

Constructions are further known from the clothing industry comprising three layers of material, of which two layers enclose a third, liquid-absorbing layer. Such sandwich constructions, however, are not designed to provide a cooling effect but, for example, an aesthetic effect or heat insulation. The liquid-absorbing property is indeed an incidental characteristic in such a sandwich construction.

It is a disadvantage of the known cooling elements that the manufacture of satisfactorily operating products is difficult and expensive. This is the case in particular in relation to mass manufacture.

It is an object of the invention to provide an improved cooling element of the type described above.

To achieve this object, the invention offers a cooling element as defined in claim 1.

Due to the presence of thermoplastic plastic, in particular polyurethane, polypropylene or polyethylene, it becomes possible to obtain a high vapour-transmittance while maintaining the weldability of the two foil layers. As a result of the weldability, e.g. by ultrasonic welding, it is possible to apply a low-cost and efficient production process. Before, in the state of the art, the foil layers were either made of weldable materials having a lower vapour-transmittance, or were not weldable and were glued or stitched together.

Glued and stitched connections are unfavourable, because they show leaks, immediately, or after some time. A glued connection also requires a curing period during manufacture, which causes the overall production process to take much longer than in the case of a welded connection.

If the connection between the two layers of foil material is achieved by means of welding on the other hand, the connection will be mechanically reliable, leak-proof, and ready substantially immediately after the actual welding operation, so that the cooling element can receive its finishing treatment immediately afterwards.

Furthermore, it is possible to control the rigidity of the obtained cooling element, in fact a prefab panel, in a given direction by choosing the welded the positions and orientations of the seams: parallel to, or even coincident with, bending lines of the cooling element. The welded seams are thus at the same time folding seams.

In an embodiment, the two layers of foil material comprise a plastic with a moisture-vapour transmittance of more than 3800 g/m2/24 h, in particular 4000 g/m2/24 h, according to the testing norm ASTM E96-BW, at a water resistance of a water column of at least 4700 mm, in particular 5000 mm, according to the testing norm ISO 811.

In another embodiment, the layers of foil material comprise a plastic of welding tear resistance of at least 15 kg/3 cm, in particular 20 kg/3 cm, (at 3.175 mm RF tear), a value determined according to the testing norm FS191A method 5970.

It is advantageous to embed between the foil layers an intermediate layer of liquid-absorbing, vapour-releasing material. Such an intermediate layer enables a more even distribution of the liquid present in the compartment, and thus enhances the cooling function of the cooling element.

Thereby, the intermediate layer itself should advantageously be distributed over the compartment, without crumbling, etc. Manners in which this may be provided are:

-   -   securing the intermediate layer at one or more locations where         the layers of foil material are welded together by positioning         the intermediate layer around the welds;     -   securing the intermediate layer at one or more locations where         the layers of foil material are welded together by constituting         at least one of the welds through a part of the intermediate         layer and blending the weld at least locally around the material         of the intermediate layer; and     -   applying an intermediate layer that also comprises a weldable         material and welding this layer at least locally to both layers         of foil material.

The latter manner has the advantage that the cooling element can be manufactured more easily because it is no longer necessary to bring the intermediate layer into the correct fitting shape beforehand. The intermediate layer is simply inserted between two foil layers, whereupon the welded seams are applied in any location as desired.

In another embodiment, additional welded connections are provided between said layers of foil material within the circumference of said compartment. This keeps the foil materials better together than if only the edges necessary for forming a compartment are welded together. The additional welded connections make the overall assembly stronger and prevent the intermediate layer becoming folded or crumpled, whereby it would no longer extend over the entire surface area.

Preferably, the welded connections—additional or not—are rounded at their corners and/or ends. This leads to fewer stress concentrations in the foil material adjacent the rounded welded connections, so that the formation of tears upon deformation of the cooling element during the use thereof is counteracted.

It is also possible that an additional layer of weldable foil material is applied between or against said two layers of weldable material at the area of at least one of the welded connections. This layer compensates for the loss of thickness that arises owing to the welding and compression process, the advantages being that a local weakening is counteracted and a more attractive appearance is obtained.

In yet another embodiment, furthermore, a protective layer of moisture-transmitting material is provided against the at least one layer of vapour-transmitting foil material by means of a welded joint at the side thereof that faces away from the intermediate layer. This embodiment has the advantages that it is more resistant to impacts from pointed objects and the like.

The invention further relates to a cooling element comprising two layers of foil material, between which layers an intermediate layer of liquid-absorbing, vapour-releasing material is accommodated, said two layers of foil material being fastened to one another by means of connections such that a compartment is formed between them, while at least one of said layers of foil material is vapour-transmitting over at least a portion of its surface area, characterized in that said compartment is in liquid communication with a buffer reservoir via at least one flow restriction.

In this manner, a dispensing of the liquid over time is possible, in various manners. It is advantageous in this case to form said buffer reservoir adjacent to said compartment between the two layers of foil material and to separate said compartment from buffer reservoir by a welded seam in which said flow restriction is provided in the form of at least one liquid passage.

In an embodiment, the buffer reservoir has a maximal volume essentially equal to the liquid volume of the liquid absorbing vapour-releasing material when this material is saturated with liquid. As such, it will help to obtain precisely one filling of the liquid-absorbing vapour-releasing material, typically a wick, without making the cooling element thicker than necessary to fill the wick. If more water would be added, water pockets could arise, in certain constructive variants of the cooling element. The welds and fixed wicks of some embodiments mentioned above cooperate with the described size of the buffer reservoir to provide optimal cooling effect.

Yet in another embodiment, the buffer reservoir has a larger content, suited to maintain the cooling function of the compartment during essentially longer time period than the maximal liquid volume of the liquid absorbing vapour-releasing material does when this material is saturated with liquid. This advantageously provides the cooling function for a longer time. Here, the welds and fixed wicks of some embodiments mentioned above may be used to optimize the cooling effect itself.

Further, the flow restriction may be realized as an opening between two welding seams that are in line, in which the head ends of said seams adjacent to the flow restriction are rounded.

Finally, the invention relates to a cooling element according to one of the claims 1-10 and one of the claims 11-15. Such a cooling element combines the advantages of both claims. In this cooling element, the advantages of the foils being made of thermoplastic plastic also apply to the buffer reservoir and the flow restrictions, which may be produced in one and the same low-cost welding cycle.

The invention will now be explained in more detail with reference to the accompanying figures, in which corresponding components have been given the same reference numerals, wherein:

FIG. 1 is a plan view of a cooling element according to the invention, and

FIG. 2 is a cross-sectional view taken on the line A-A of the cooling element of FIG. 1.

The cooling element shown in FIG. 1 comprises two layers of foil material 1 and 2 between which an intermediate layer 3 of a liquid-absorbing, vapour-releasing material is arranged. The two layers of foil material 1 and 2 are fastened to one another by means of welded connections 4 such that a compartment 5 is formed between the two layers of foil material 1 and 2 and the welded connections 4. The layer 2 of foil material transmits no liquid but does transmit vapour. The layer 1 of foil material blocks both liquid and vapour in this example, but it may be vapour-transmitting in an alternative embodiment. The layers of foil material 1 and 2 are made from thermoplastic polyurethane, a weldable thermoplastic plastic, and are welded at the areas of the elongate fusion seams 4 together with the intermediate layer of material 3.

In this example, the two layers of foil material comprise a plastic with a moisture-vapour transmittency of more than 3800 g/m2/24 h, in particular 4000 g/m2/24 h, according to the testing norm ASTM E96-BW, at a water resistence of a water column of at least 4700 mm according to the testing norm ISO 811. Further, the two layers of foil material have a welding tear resistance of at least 15 kg/3 cm (3.175 mm RF tear), in particular 20 kg/3 cm, determined according to the testing norm FS191A method 5970.

The intermediate layer 3 is also formed from a weldable material, in the present case comprising thin threads formed into a sponge-like layer. The intermediate layer is compressed and welded together at the areas of the welded seams 4 such that it has become very thin and the layers of foil material 1 and 2 are substantially in contact with one another, as is clearly shown in FIG. 2. In a modification (not shown) of the embodiment shown in FIGS. 1 and 2, the intermediate layer is formed from woven natural cotton and is interrupted at the areas of the seams.

The layers of foil material 1 and 2 extend beyond the fusion seams 4 to outside the compartment 5 so as to form a circumferential edge 6 that can be used for sewing the cooling element to an object to be cooled, a rucksack in this example.

FIG. 1 also shows further welded connections 7 provided between said layers of foil material within the circumference of said compartment. These welded connections ensure in particular that the layers of foil material 1 and 2 and the intermediate layer 3 stay close together, which makes for an easier handling of the cooling element and renders it less vulnerable.

The welded connections 4 and 7 are rounded at some of their corners and ends. It is prevented thereby that stress concentrations and eventually tears will arise when the cooling element is bent, as happens in normal use of a rucksack.

The compartment 5 adjoins a buffer reservoir 8 which is also formed between welded seams 4 and layers of foil material 1 and 2 but which does not comprise an intermediate layer 3. The buffer reservoir 8 has a round fill opening 10 that is provided with an external screw-thread (not shown), on which screw-thread a closing cap (also not shown) can be turned so as to close off the reservoir 8 in a liquid-tight manner. The fill opening 10 is welded by an edge 11 thereof to the layer of foil material 2.

Three flow restrictions 9 in the form of interrupttions in the welded seam 4 are provided between the buffer reservoir 8 and the compartment 5. The flow restrictions 9 have dimensions so narrow that they limit the flow through them and thus prevent the buffer reservoir from emptying itself instantly substantially completely into the compartment 5. This emptying is also counteracted by the presence of the additional welded seams 7 mentioned above, which ensure that the volume of the compartment 5 is limited such that no fresh liquid is admitted until after liquid has evaporated through the layer of foil material 2.

In this example, the buffer reservoir serves as a functional buffer, since it has a maximal volume more much higher than the liquid volume of the intermediate layer 3 when this layer is saturated with liquid. Alternatively, not shown, it will serve as a filling buffer, when its volume is more or less equal to the liquid volume of the intermediate layer. Also not shown is a variant in which a buffer reservoir is provided that is connected to the compartment 5 by means of a tube that serves as a flow restriction, and wherein the reservoir is not made as a single whole with the compartment but as two distinct units.

The intermediate layer of liquid-absorbing, vapour-releasing material 3 in this embodiment is at the same time an inhibitor to fungal and bacterial growth in that it has been impregnated with a liquid which after drying forms a covering layer that protects against the growth of fungi and bacteria.

The operation of the embodiment described is based on the evaporation of liquid from the intermediate layer 3 in the compartment 5 owing to the supply of heat through the layer of foil material 1 and the discharge of the moisture arising from said evaporation through the layer of foil material 2. Fresh liquid is supplied from the buffer reservoir 8 through the openings in the welded seam 4 that serve as a flow restriction 9. The buffer reservoir 8 is filled up, if necessary, through the closable fill opening 10 provided therein.

Modifications of the embodiment described above are possible. Thus, for example, a protective layer of moisture-transmitting material may be provided over the layer of vapour-transmitting foil material 2 at the side thereof facing away from the intermediate layer and be connected thereto by means of a welded joint or by lamination. 

1-16. (canceled)
 17. A cooling element comprising: two layers of a foil material that may or may not be flexible, the two layers of foil material being fastened to one another by welding connections such that a compartment closed for liquid is formed between them and at least one of the layers is vapor-transmitting over at least a portion of its surface area, wherein the two layers of foil material comprise thermoplastic plastic, or polyurethane, or polypropylene, or polyethylene.
 18. A cooling element according to claim 17, wherein the two layers of foil material comprise a plastic with a moisture-vapor transmittance of more than 3800 g/m2/24 h, according to testing norm ASTM E96-13W, at a water resistance of a water column of at least 4700 mm according to testing norm ISO
 811. 19. A cooling element according to claim 17, wherein the layers of foil material comprise a plastic of welding tear resistance of at least 15 kg/3cm, or 3.175 mm RF tear, determined according to testing norm FS191A method
 5970. 20. A cooling element according to claim 17, further comprising, between the foil layers, an intermediate layer of liquid-absorbing, vapor-releasing material.
 21. A cooling element according to claim 17, wherein the intermediate layer is secured at one or more locations where the layers of foil material are welded together by positioning the intermediate layer around the welding connections.
 22. A cooling element according to claim 17, wherein the intermediate layer is secured at one or more locations where the layers of foil material are welded together by constituting at least one of the welding connections through a part of the intermediate layer and blending the welding connections at least locally around the material of the intermediate layer.
 23. A cooling element according to claim 17, wherein the intermediate layer further comprises a weldable material and is at least locally welded to both layers of foil material.
 24. A cooling element according to claim 17, wherein additional welded connections are provided between the layers of foil material within the circumference of the compartment.
 25. A cooling element according to claim 17, wherein an additional layer of weldable foil material is applied between or against the two layers of weldable foil material at an area of at least one of the welded connections.
 26. A cooling element according to claim 17, further comprising a protective layer of moisture-transmitting material provided against at least one layer of vapor-.
 27. A cooling element comprising: two layers of foil material, between which layers an intermediate layer of liquid-absorbing, vapor-releasing material is accommodated, the two layers of foil material being fastened to one another by connections such that a compartment is formed between them, while at least one of the layers of foil material is vapor-transmitting over at least a portion of its surface area, wherein the compartment is in liquid communication with a buffer reservoir via at least one flow restriction.
 28. A cooling element according to claim 25, wherein the buffer reservoir is formed adjacent to the compartment between the two layers of foil material and is separated therefrom by a welded seam in which the flow restriction is provided in a form of at least one liquid passage between the compartment and the buffer reservoir.
 29. A cooling element according to claim 27, wherein the buffer reservoir has a maximal volume essentially equal to liquid volume of the liquid absorbing vapor-releasing material when this material is saturated with liquid.
 30. A cooling element according to claim 27, wherein the buffer reservoir has a content configured to maintain a cooling function of the compartment during an essentially longer time period than a maximal liquid volume of the liquid absorbing vapor-releasing material does when this material is saturated with liquid.
 31. A cooling element according to claim 27, wherein the flow restriction is realized as an opening between two welding seams that are in line, in which head ends of the seams adjacent to the flow restriction are rounded. 